1. Field of the Invention
The present invention relates generally to network cabling systems and methods and, more particularly, to the continual cable thermal monitoring using cable resistance considerations for power over Ethernet (PoE) applications.
2. Introduction
The IEEE 802.3af PoE standard provides a framework for delivery of power from power source equipment (PSE) to a powered device (PD) over Ethernet cabling. In this PoE process, a valid device detection is first performed. This detection process identifies whether or not it is connected to a valid device to ensure that power is not applied to non-PoE capable devices. After a valid PD is discovered, the PSE can optionally perform a power classification. IEEE 802.3af defines five power classes for a PD device. The completion of this power classification process enables the PSE to manage the power that is delivered to the various PDs connected to the PSE.
This PoE application is a relatively new application that is being applied to an existing cabling infrastructure. Significantly, this cabling infrastructure was not originally designed for the distribution of power. Accordingly, the provision of power over the cabling infrastructure can introduce unintended effects such as heat. This heat can be generated through the transmission of current in the cable itself or in surrounding cables. The dissipation of this heat can be constricted due to physical constraints such as conduits, poor air circulation, etc. PoE systems must account for this heat must be accounted for during operation. These considerations are likely to play an even greater role in the administration of high-power PoE systems such as that proposed by the IEEE 802.3at specification. What is needed therefore is a mechanism that enables the PoE system to account for the existence of heat in the cabling infrastructure in an active manner.